1. Field
One embodiment of the invention relates to a sound quality correction apparatus, a sound quality correction method and a sound quality correction program to execute the sound quality correction process adaptively for a speech signal and a music signal contained in an audio signal (audio frequency) to be reproduced.
2. Description of the Related Art
As is well known, in the broadcast receiver configured to receive the TV broadcast and the information reproduction device configured to reproduce the recorded information, for example, the process of correcting the sound quality is executed on the audio signal reproduced from the received broadcast signal or the signal read from an information recording medium in order to further improve the sound quality.
The sound correction process executed on the audio signal in such a case is varied according to whether the audio signal is a speech signal representing the speech of a person or a music (non-speech) signal representing a musical composition. Specifically, the quality of the speech signal in a talking scene, the on the sport broadcasting, etc., is improved by executing the sound quality correction process in such a manner as to emphasize and clarify the center localization component, while the sound quality of a music is improved by executing the sound quality correction process on the music signal in such a manner as to secure the expansion by emphasizing the stereophonic effect.
For this purpose, a technique has been studied whereby whether the acquired audio signal is a speech signal or a music signal is determined and, in accordance with the result of this determination, a corresponding sound quality correction process is executed. In the actual audio signal, however, the speech signal and the music signal often are mixed, and the process of identifying them is difficult. Under the circumstances, therefore, no appropriate sound quality correction process is executed on the audio signal.
Jpn. Pat. Appln. KOKAI Publication No. 7-13586 discloses a configuration in which the input sound signal is classified into three types including a “speech”, a “non-speech” and an “undetermined” by analyzing the zero-crossing rate and the power fluctuation thereof, so that the frequency characteristic of the sound signal is maintained at a characteristic emphasizing the speech band upon determination as a “speech”, a flat characteristic upon determination as a “non-speech”, and the characteristic determined in the preceding session upon determination as an “undetermined”.